A power shovel is a type of excavation machine that has been used for decades to dig or extract material from a work site. Power shovels are commonly used for the excavation and removal of ore and/or overburden in mining operations, although they are also used in other applications as well.
While power shovels come in a wide range of sizes and configurations, most involve a cab or “house” that is pivotally mounted to an undercarriage assembly. The undercarriage assembly may be provided with a plurality of tracks or wheels to allow the shovel to be moved from place to place. A crane or boom member mounted to the cab is supported in an elevated position by means of one or more suspension ropes. The boom supports a stick or handle member having a bucket or dipper mounted on the end thereof. The handle member is moveably mounted to the boom via a saddle block assembly that allows the handle member to pivot and translate with respect to the boom. Pivotal movement of the handle is typically accomplished by means of one or more hoist ropes connected to the dipper. Translational movement of the handle with respect to the boom, commonly referred to as “crowd,” is typically accomplished via a rack and pinion gear set provided on the saddle block assembly, although other arrangements are known and may be used.
Most power shovels are electrically operated, with various types of electric motors being used to move or operate the various elements of the shovel to pull the dipper through the material to be excavated and thereafter deposit the excavated material contained in the dipper at a suitable location (e.g., into the bed of a haul truck). A typical work cycle for a power shovel involves four primary phases or steps, commonly referred to as digging, swinging, dumping, and returning. The digging phase consists of “crowding” the dipper into the bank, hoisting the dipper to fill it, then retracting it from the bank. Once the dipper is clear of the bank, the dipper is moved through a swing path (i.e., by rotation of the cab with respect to the undercarriage) until it is positioned over the designated dump location. During the dumping phase, the dipper door is opened to dump the load. Thereafter, the dipper door is closed and the dipper returned to position adjacent the bank for the next work cycle.